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Biology · Class 12
Individuals vary, some variation is heritable, more offspring are produced than survive, and carriers of advantageous variants leave more descendants.
PracticeLight, water, temperature, soil and chemicals are abiotic factors; competitors, predators, prey, parasites and mutualists are biotic factors.
PracticeAn adaptation is a heritable feature shaped by selection for a function. Fitness means relative reproductive contribution in a particular environment, not physical strength.
PracticeAdaptive immunity uses specific lymphocyte receptors, clonal expansion and memory. B cells produce antibodies; T cells coordinate responses or kill infected cells.
PracticeFood security requires reliable access to safe nutritious food. Crop improvement, soil care, efficient water use, storage and biological pest control can raise sustainability.